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Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Revenue, Major Customer [Line Items]        
Revenues $ 7,322 $ 7,689 $ 16,069 $ 17,166
Revenue from Related Parties 1 0 2 0
Commonwealth Edison Co [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,417 1,351 2,856 2,759
Revenue from Related Parties 11 5 16 9
Commonwealth Edison Co [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (25) (14) (13) (42)
Commonwealth Edison Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,442 1,360 2,863 2,789
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (25) (9) (7) (30)
PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenues 681 655 1,493 1,554
Revenue from Related Parties 2 2 4 3
PECO Energy Co [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 4 (3) 5 (6)
PECO Energy Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 678 652 1,485 1,553
PECO Energy Co [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 3 3 8 1
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Related Parties 1 1 3 2
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Related Parties 0 0   1
Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 616 649 1,554 1,625
Revenue from Related Parties 4 6 10 12
Baltimore Gas and Electric Company [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (37) 6 0 17
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 652 639 1,550 1,599
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (36) 10 4 26
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Related Parties 3 1 6 1
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Related Parties 1 4 4 9
Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,016 1,091 2,187 2,319
Revenue from Related Parties 3 3 7 7
Pepco Holdings LLC [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (64) (3) (47) 12
Pepco Holdings LLC [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,080 1,091 2,233 2,302
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (64) 0 (46) 17
Potomac Electric Power Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 494 531 1,039 1,106
Revenue from Related Parties 1 1 3 3
Potomac Electric Power Company [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (13) (1) 2 13
Potomac Electric Power Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 507 530 1,036 1,089
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (13) 1 3 17
Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 267 287 617 667
Revenue from Related Parties 2 2 4 3
Delmarva Power and Light Company [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (25) 0 (24) 1
Delmarva Power and Light Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 292 286 640 665
Delmarva Power and Light Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (25) 1 (23) 2
Atlantic City Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 256 274 532 547
Revenue from Related Parties 1 1 1 1
Atlantic City Electric Company [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (26) (2) (25) (1)
Atlantic City Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 282 276 557 548
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (26) (2) (25) (1)
Electricity, US Regulated        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3,475 3,512 7,222 7,343
Electricity, US Regulated | Commonwealth Edison Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,431 1,360 2,853 2,792
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,442 1,360 2,863 2,789
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 5 6 12
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 767 647 1,468 1,356
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 327 349 689 709
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 119 127 253 259
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 11 10 23 23
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 218 227 430 442
Electricity, US Regulated | PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 580 567 1,180 1,188
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 582 563 1,181 1,184
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 6 3 7
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 377 343 759 752
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 88 99 187 195
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 55 52 108 100
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 7 7 14 14
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 55 62 113 123
Electricity, US Regulated | Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 530 540 1,125 1,191
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 532 538 1,128 1,188
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1 3 3 6
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 304 282 644 667
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 51 59 118 129
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 94 109 198 219
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 7 6 14 13
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 76 82 154 160
Electricity, US Regulated | Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,047 1,067 2,133 2,205
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,050 1,067 2,139 2,207
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 3 1 5
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 529 494 1,062 1,073
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 105 120 221 241
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 240 278 493 545
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 15 16 31 31
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 161 159 332 317
Electricity, US Regulated | Potomac Electric Power Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 506 531 1,034 1,090
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 507 530 1,036 1,089
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 2 1 4
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 237 224 472 480
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 29 35 65 73
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 175 207 363 411
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 8 8 17 17
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 58 56 119 108
Electricity, US Regulated | Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 260 261 543 568
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 262 262 546 570
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 1 1 1
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 147 135 308 320
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 39 44 82 93
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 22 25 45 49
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 4 6 7
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 51 54 105 101
Electricity, US Regulated | Atlantic City Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 281 275 556 547
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 282 276 557 548
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 145 135 282 273
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 37 41 74 75
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 43 46 85 85
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 4 4 7 7
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 53 50 109 108
Natural Gas, US Regulated        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 236 218 832 883
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 95 89 304 369
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 96 89 304 369
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (1) 0 0 0
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 70 49 220 247
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 19 33 70 105
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 1
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 6 6 12 13
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1 1 2 3
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 119 97 419 405
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 120 101 422 411
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 1 1 3
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 81 60 287 279
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 12 11 46 46
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 24 23 76 73
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 7 13 13
Natural Gas, US Regulated | Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 30 24 94 95
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 30 24 94 95
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 17 11 57 55
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 8 7 25 26
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1 2 2 3
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 3 7 7
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1 1 3 4
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 30 24 94 95
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 30 24 94 95
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 17 11 57 55
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 8 7 25 26
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1 2 2 3
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 3 7 7
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1 1 3 4
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax $ 0 $ 0 $ 0 $ 0